This report includes twelve tables with hundreds of crash reduction factors and crash reduction functions (CRF). CRFs are a value that represents the percent reduction in crashes. For example, a CRF of 20 equates to 20 percent crash reduction. Negative CRFs imply an increase in crashes. These tables are organized into categories for intersection, roadway departure, and pedestrian crashes, and contain information from the source research studies such as the targeted crash type and severity, AADT range, and study design. These CRFs can be used to estimate the change in crashes as a result of implementing countermeasures.

Note that this tool was published prior to the publishing of the AASHTO Highway Safety Manual 1st Edition and the FHWA Crash Modification Factor Clearinghouse, which both use the convention of crash modification factors (CMFs) rather than CRFs. CMFs are multipliers that also represent a percent change in crashes; however they are expressed as a proportion relative to the before crashes. For example, a CMF of 0.80 equates to a 20 percent crash reduction. CMFs above 1.0 imply an increase in crashes.